Generally, dimming technology can be divided into Pulse Width Modulation (PWM) dimming and amplitude-modulation (AM) dimming. In PWM dimming, the current of the light source consists of high and low levels and has a frequency of about 1 kHz. Accordingly, for specific situations or products (e.g., photographing, screen and etc.), the PWM dimming causes dark region and visual flicker. On the other hand, in AM dimming, when the magnitude of loading varies significantly, the driving circuit may produce an unstable light source current due to the too-low duty cycle, which flickers the light and limits the dimming range of AM dimming.
Therefore, there is a need for providing a dimming technology to make circuits have larger dimming range under a simple, low-interference and low cost configuration.